Fix rust binding build script (#59)

Author: the-mikedavis

bindings/rust/build.rs

@@ -9,8 +9,11 @@ fn main() {
         .flag_if_supported("-Wno-trigraphs");
     let parser_path = src_dir.join("parser.c");
     c_config.file(&parser_path);
+    println!("cargo:rerun-if-changed={}", parser_path.to_str().unwrap());
 
     let scanner_path = src_dir.join("scanner.c");
     c_config.file(&scanner_path);
     println!("cargo:rerun-if-changed={}", scanner_path.to_str().unwrap());
+
+    c_config.compile("parser-scanner");
 }